Importing an exported project fails with "wrong argument type nil"

Importing a project from CE to GitLab.com fails with "wrong argument type nil" and no other explanation.

Steps to reproduce

  1. Export an existing projects (Settings -> Export project) and download the *.tar.gz

  2. Create a new project on another server and choose "Import project from: GitLab export"

  3. Choose the previously downloaded *.tar.gz and click on "Import project"

Example Project

Private project accessible through internal google drive.

What is the current bug behavior?

After clicking on "Import project", the following error appears:

The repository could not be imported.
Error importing repository  into <PROJECTPATH> - wrong argument type nil

What is the expected correct behavior?

The project is imported successfully and contains all data as at the time the export was created.

/cc @jameslopez